1. Field of the Invention
The invention relates to a motor vehicle antenna device.
2. Description of the Related Technology
An example of one such motor vehicle antenna device is disclosed in DE 37 19 692C2. One version of its practical implementation is for Mercedes Benz passenger cars of series W 210, wherein a radio frequency device, which contains matching circuits and amplifiers, is attached to the body. The device is connected via cables to contact sites of the antenna structure(s) located on the edge of the window. The cables are either detachably plugged into or permanently soldered the contact sites of the window and to the radio frequency device.
These contacts must compensate for all tolerances between the body and the front or rear window of the vehicle, which are connected by flexible cement. These tolerances are due to shaking movements of the vehicle, and form in the production of contacts, installation of the window and radio frequency device.
The contact sites of the antenna structures are produced, among others, as a silver print relative to the window edge of the window relative to the body. The tolerances of the contact sites of the antenna structures dictate relatively large contact surfaces which are unfavorable in terms of radio frequency technology.
The antenna parameters are influenced by the laying of the connecting cables. The terminal impedance of the antenna is especially influenced by which on the input side high tolerances, which must likewise be balanced, arise, in the radio frequency device. Moreover, all the solder on the vehicle window is a problem. The solder leads to high glass fracture rates as a result of pre-stress and poor thermal conductivity of the glass, and thus makes the system more expensive.
EP 0 386 678B1 furthermore discloses attaching active quadripoles. The quadripoles are intended to be connected to the antenna structures by soldering or cementing securely on the vehicle window. In this arrangement, tolerances between the vehicle window and the body need not be balanced. In addition, no vibration tolerances need to be balanced between the two when the vehicle is moving. This is due to the lack of motion of the radio frequency device relative to the body of the vehicle.
This prior art device is not suited for the repairs or replacement of the radio frequency device, because of the need for unsoldering and resoldering the repaired or replaced radio frequency device or the need to completely replace of the window is necessary.
In addition, it is necessary to connect the quadripole to the antennas by line and solder connections. The line and solder connections result in increased cost and the aforementioned danger of window breakage.
An object of the invention is to devise a vehicle antenna device in which the radio frequency device can be detachably fastened to the window as simply and economically as possible. Moreover, this device can be connected electrically to the connection sites of the antenna structure(s) without connecting lines and without soldering.
This object is achieved by the present invention. The tolerances and relative movements between the body and the window are insignificant due to the detachable arrangement of the radio frequency device to the vehicle window. Additionally, only the tolerances of the silver print, which are one order of magnitude less, need be balanced and thus replacement of the devices can be done easily and promptly. This is advantageous because it can be done for repair purposes or for use of different radio frequency devices matching to the altered conditions. In addition, it is also possible to provide the same base for a series of vehicles, and to then equip depending on the vehicle type or antenna type. The base may be equipped with a matching radio frequency device with an external form which is always the same with reference to secure holding, as matched to the base, and its contact schematic corresponds to the configurations of the respective connection sites.
The device as claimed in the invention is thus much more versatile compared to the described prior art. Additionally, changing the device does not require expensive replacement of the window.
Various electronic components can be used as the radio frequency device and matched to the requirements of the individual case. Generally, it is an amplifier with a matching circuit. However, when only a small window surface (which does not interfere with the view of the driver) is available, a circuit may be connected to a receiver or transmitter via a ribbon cable. This connection can either be a direct connection, or one via an amplifier mounted on the body of the car.
Furthermore, the radio frequency device, for example an amplifier, can therefore be connected directly, i.e., without a connecting line to the antenna base point. This is beneficial for both independently matching the structure of the vehicle and for reception, where optimal signal/noise ratio is achieved at the amplifier output. A matching element is not necessary in the case of transmission due to the direct connection of the radio frequency device to the antenna structure(s). Optimal transmitter power is available by matching the amplifier output to the base point impedances of the antenna structures transformed to the contact sites.
Advantageous versions and embodiments of the vehicle antenna device according to the invention are set forth and claimed herein.
For electrical connection of the radio frequency device to the contact points of the antenna structure(s) there is an especially simple version which is economical to produce involving direct connection of the device terminals to the contact sites. The base need not have any contact devices, and simply serve as a holding device, and thus can be produced extremely economically as a simple injection molding.
An alternative solution for the electrical connection of the radio frequency device and the antenna(s) involves direct connection of the device terminals installed in the base to the contact cites. This solution is more complex, due to the additional contacts in the base, but offers great diversity of structural configuration versions. There are possibilities of adaptation to different spatial circumstances.
By combining the contact points of several antenna structures which have been impressed on the windshield, for example for several frequency ranges and/or diversity reception, in a terminal panel of small area, the already low silver print tolerances are further reduced. According to the invention, the contact sites can be limited to a relatively small area (unlike as in the prior art, where according to DE 37 19 692L2, they are arranged around the entire vehicle window) thereby lowering cost. In this way the size of the base and the resulting adverse effect on vision can be minimized or the base can be located in an advantageous manner, for example under moldings of the vehicle.
Here it is especially favorable to execute the feeder lines from the base points of the antenna structures to the contact sites of the termination panel by coplanar lines. Coplanar lines can be easily produced and transmit good electrical data. The production of the coplanar lines with the silver printing of the antenna structures is especially economical and precise. This also applies to the markings which are provided for the positioning of the base. These markings enable prompt and accurately positioned attachment of the base on the vehicle window, which in turn allows exact assignment of the contacts of the radio frequency device to the contact sites and thus reliable contact-making for holding of the radio frequency device in the base. A series of technical approaches are possible for holding the device. A version which is simple in structure and production uses inwardly projecting projections on the frame of the base and corresponding outwardly projecting lugs on the radio frequency device to allow the device to be held in the base after installation.
Preferably the radio frequency device is pushed into the base until the lugs of the radio frequency device which project to the outside have been fully inserted under the projections of the base frame.
Advantageously the projections and lugs are located on three corresponding sides of the base or the radio frequency device. With this location, the radio frequency devicexe2x80x94especially when the projections on each frame side are made continuousxe2x80x94can be inserted into a type of pocket of the base.
To do this, sufficient space on the insertion side on the order of the insertion path, is necessary. One preferred installation of the base is in the edge area of the vehicle window, although generally there is not enough room available. For this case it is a better idea to interrupt the projections on the side opposite the insertion side. In other words, to provide several projections on each of the three sides. This embodiment is advantageous and saves material. The radio frequency device is inserted first perpendicular to the surface of the base into the letter, the lateral lugs of the radio frequency device sliding between the lateral projections of the base, and then inserted perpendicularly thereto into the base until it stops, whereby all lugs lie under the pertinent projections.
In the first installation step, the radio frequency device simply projects by roughly the depth of the projections beyond the insertion side. This embodiment is especially well suited for installation on the window edges because of the smaller space requirement.
The invention provides that the radio frequency device be held by means of a detachable catch holder. Advantageously, in the mounted state it is resistant to vibration. It is especially simple and economical to make this catch, both with respect to production and also operation. The snap-in pins with the catch cams can be produced without additional cost, as, for example, in an injection molding process (preferably together with the base).
The catch cams are pressed down when the radio frequency device is inserted into the base. When the radio frequency device has been fully inserted (as a result of the spring action of the snap-in pins) they snap back into their initial position, thus fitting behind the housing of the radio frequency device. On the other hand, by pressing down the catch cams, the radio frequency device can be easily dismounted and pulled out of the base.
Insertion of the radio frequency device into the base is greatly facilitated by the slide bevels provided on the lugs and projections which correspond to the facing ends. In many cases it is enough to bevel either only the projections or only the lugs. However, when producing the base and the housing of the radio frequency device, in an injection molding process, for example, the lugs and the projections can be produced without added costs with the corresponding profiles.
A detachable electrical connection of the terminals of the radio frequency device to the pertinent contact sites of the antenna structures on the vehicle window is done in one especially advantageous embodiment of the vehicle antenna device according to the invention by contact springs which are attached to the radio frequency device. They ensure not only permanently secure contact, which can be released if necessary without any effort, but at the same time press their lugs by their spring force against the bottom of the projections which accommodate the spring force. Both sufficient contact pressure and thus vibration-proof contact-making as well as prevention of rattling noise are achieved by suitable shaping and choice of the material of the contact springs in an extremely simpler manner.
Another possibility for increasing the contact pressure of the contact springs on the contact sites without added cost is to provide the lugs and/or projections with another bevel towards the housing of the radio frequency device. When the radio frequency device has been fully inserted into the base, the lugs, and thus the contact springs attached to the radio frequency device, are pressed further towards the vehicle window by the second slide bevel. Basically the contact springs can be attached anywhere on the surface of the radio frequency device facing the base; they need simply to lie exactly opposite the corresponding contact sites of the antenna structures. When the contact springs are aligned in a line, simple and accurate positioning is achieved. An example is alignment between the projections on the wide side (contact side) of the base.
When the contact springs are arched in their lengthwise direction, therefore the insertion direction, the result is advantageous. Making arched contact springs results in spot and thus defined contact with high contact pressure, and also allows careful sliding into the silver print of the contact points. In turn, repeated removal and insertion of a radio frequency device into and out of the base is more secure. Alternatively, if the contact springs are arched in their transverse direction in addition to moving the radio frequency device and thus the contact springs in their lengthwise direction, advantageous convex arching in this transverse direction results.
The contact springs could consist of conductive plastic in the form of plastic pads (due to their short length the electrical resistance is still relatively low) or of metal coated plastic. Metal springs have the advantage of higher stability or fracture safety, greater possible contact pressures and better conductivity. In addition, they can be produced in any shape more easily and economically than punched bending parts.
One embodiment of the contact springs is especially suited for electrical connection to circuit boards and retention in potted boards. In this embodiment, leaf springs are made roughly u-shaped with a flat leg which is mechanically and elastically connected in the radio device (preferably on a circuit board) and a convexly-arched leg which adjoins under pressure the contact sites. If the flat leg is under than the arched leg.
The execution is characterized by high mechanical stability and a large solder area for simple and reliable contact-making on the circuit board.
For exact positioning of the flat spring arm on the board for the soldering and optionally the potting or extrusion coating process, it is especially advantageous to provide the free end of the flat leg with a bent projection which is inserted into an assigned recess of the circuit board for mounting.
As protection against mechanical damage and weather effects it is advantageous to provide the radio frequency device with a housing. To reliably prevent short circuits it comprises insulating material. Production is especially economical when the housing comprises extrusion coating or potting material. This housing can be produced easily in all possible forms, without additional costs, with retaining lugs, and does not require special holding means for the injected parts (such as for example the contact spring. Furthermore, the housing can be produced especially flat, enabling hidden installation under moldings of the vehicle such as the head liner, the hat rack or the C column covering.
Another advantage of a plastic cast housing is that additional devices, for example holding or guiding means, such as molded-in cable receivers for feeder lines of other antennas (cellphone antennas or GPS navigation antennas) can be integrated essentially without additional costs in production.
The radio frequency device is not tied to the size of the base with respect to its dimensions. Rather it can also project easily over the base with parts which have no contacts, if the holding force of the lugs which fit behind the projections of the base is sufficient.
If this is not the case, for example when an especially high vibration resistance is demanded, widening of the base beyond its terminal area assigned to the termination panel of the antenna structures is advantageous. Here the lateral projections are feasibly made as individual projections spaced apart from one another, between which the lateral lugs of the widened part of the radio frequency device are inserted, or on the third side, or there can also be a continuous projection.
The entire base can be made in several parts (but as one piece), with the advantage that only one base for the different sizes of the devices is necessary. The vehicle antenna device is thus economical and versatile because (due to this base design) different devices (for example single-stage or multistage amplifiers and passive circuits such as filters, matching circuits or remote feed means) do not require different windows.
The cementing of the base on the vehicle window is permanently secure, promptly exact, and can be done with much less effort than solder connections.
Even relatively complex radio frequency devices can be produced today with comparatively small dimensions. Nevertheless in the interest of maximum possible driving safety it is advantageous to position the base on the edge of the window. As previously mentioned, if somehow possible, place it under moldings of the vehicle or under the surfaces of the window covered by the black print.
The invention is detailed below in the figures using one embodiment of the vehicle receiving antenna device as claimed in the invention with a widened base and an amplifier.